The present invention generally relates to porous reinforcing agent clusters and composites thereof for downhole tools and related methods.
Downhole tool, e.g., drill bits, have been formed of particle reinforced metal matrix composites. The performance characteristics, e.g., strength, toughness, wear resistance, erosion resistance, and thermal resistance, of a downhole tool are thought to depend on the reinforcing agents in the metal matrix, e.g., tungsten carbide particulates dispersed in a copper alloy. Generally, larger reinforcing agents are thought to impart wear resistance to the downhole tool, while smaller reinforcing agents are thought to impart strength to the downhole tool. However, larger reinforcing agents are thought to reduce strength of the downhole tool, while smaller reinforcing agents are thought to reduce wear resistance of the downhole tool. Therefore, approaches to simultaneously enhance seemingly inversely related performance characteristics, e.g., strength and wear resistance, have been undertaken.
One approach where some success has been observed includes using bimodal size distributions of reinforcing agents to form composites by traditional methods. This approach is believed to yield homogeneously distributed bimodal reinforcing agents through a drill bit body, for instance.
A second more complex approach includes heterogeneous distributions of bimodal reinforcing agents having discrete regions of reinforcing agents. Historically, these discrete regions have been achieved by first creating solid composite particles of a large number of reinforcing agents in a metal matrix. Then, these solid composite particulates are then incorporated into a final composite just as the particulate reinforcing agents would be incorporated in standard procedures. This approach yields solid composite particles distributed homogenously throughout the drill bit body. However, this approach oftentimes introduces phase boundaries at the interfaces between the solid composite particles and the matrix of the drill bit body. If the interfaces are not properly formed or have defects, then the interfaces often become points of failure in the final downhole tool, e.g., the drill bit. Defects in the downhole tool can significantly reduce the performance characteristics of the downhole tool. For example, defects can cause: increased wearing thereby reducing the lifetime of the bit, uneven wearing thereby reducing the lifetime and efficacy of the drill bit, and/or reduced strength thereby allowing for chipping or cracking during operation of the drill bit. As the solid composite particles are large by design to create the discrete regions with a multitude of reinforcing agent clusters, the defects at the interfaces of the solid composite particles and matrix of the drill bit body can be larger and more detrimental than a defect between the drill bit matrix and a single reinforcing agent cluster.
The ability to create discrete regions of reinforcing agents while minimize the size and occurrence of failure points would be of value to one skilled in the art.